1. Field of the Invention
The present invention is related generally to medical stimulation leads. More specifically, the present invention is related to a temporary stimulation lead with polymer electrodes.
2. Prior Art
Medical stimulation leads provide a means to deliver electrical energy from an implantable medical device such as a pacemaker or neurostimulator to stimulate body tissue. Such leads are complex devices that are designed with an intricate network of conductor wires and electrodes. Medical stimulation leads can be categorized as being either a permanent medical lead or a temporary medical lead. As the name implies, permanent medical stimulation leads are placed in the body for chronic use to provide continuous long-term stimulation to cardiac or neurological tissue. On the other hand, a temporary medical stimulation lead is designed for relatively short term use in the body. Permanent medical stimulation leads are designed for long term implantation of about 6 months or more and are typically constructed with more durability than temporary medical stimulation leads.
Before a permanent medical lead system is implanted, a temporary stimulation lead is used to screen potential patients for therapy effectiveness. This saves expense and minimizes the invasiveness of the procedure to the patient until it can be proven that the system will be efficacious. Previous prior art temporary leads provide monopolar stimulation in an effort to save size and expense. The present invention provides a cost effective multi-polar temporary lead with a small diameter which creates less trauma to the patient.
Polymeric materials have previously been used to construct medical stimulation leads. Such leads utilizing polymeric materials are disclosed in U.S. Pat. No. 7,225,035 to Brabec at al., U.S. Pat. No. 6,922,588 to Kranz at al. and U.S. Pat. No. 5,667,615 to Maurer et al.
Brabec et al, in the '035 patent discloses the use of conductive polymers such as carbon filled silicone, polyacetylene, polypyrrole and polyanaline for use as an electrode material. Such materials, as stated by Brabec, provide flexibility and allow the electrode to bend in the tight spaces of the coronary vasculature.
Kranz et al. in the '588 patent discloses the use of conductive polymeric materials that have been specially processed to produce an anisotropic electrical behavior. In the '588 patent, conductive polymeric materials such as polyacetylene, polyparaphenylene, polyphenylene sulfide, polyparaphenylvinylene, polypyrrole, polyfuran, polythiophen, polyphenylamine, polyethylenedioxythiophen-polystyrene sulfonate and polyacene, are processed to produce an electrically conductive medical lead (electrode line as stated by Kranz) designed to minimize electrical radial conduction and enhance electrical conduction along the lead's longitudinal axis. As Kranz states, in column 4, line 32 of the '588 patent, “By presetting the respective polymerisation and processing conditions which are to be adapted to the respective individual case involved, it is possible to ensure that the individual polymer chains of the intrinsically conductive polymer coaxially oriented in the longitudinal direction of the electrode line 12 and there is no conductivity worth mentioning in the radial direction.” As will be discussed in more detail, the present invention is directed to the use of polymeric materials in electrodes where emission of electrical energy in a radial direction is desired.
Mauerer et al. in the '615 patent is directed to a vaginal electrode with alternating bands of conductive carbon filled silicone and non-conductive silicone rubber. Mauerer discloses an improved means of coupling electrical energy to the electrode through the use of mechanical tension to secure the lead wires to the polymeric electrodes of carbon loaded silicon rubber.
Unlike Mauerer, however, the temporary medical stimulation lead of the present invention utilizes a hydrophilic polymeric hydrogel material that acts as both an electrical stimulation electrode and a reservoir from which a therapeutic drug is eluted. Electrical energy is radially emitted from the hydrogel structure that provides therapeutic electrical stimulation to body tissue. In addition, a therapeutic drug can be emitted from the surface of the hydrophilic hydrogel material from which it is stored.
Furthermore, the present invention provides multipolar stimulation that provides increased control of the electrical stimulation as compared to monopolar prior art stimulation. In addition to the medical lead's simplified construction, the use of the conductive hydrophilic hydrogel material provides a cost effective means to stimulate tissue and elute therapeutic drugs that provide a pharmacological benefit.